Developing purinergic receptor inverse agonists for treating triple negative breast cancer - Summary We propose to develop novel adenosine receptor inverse agonists for the treatment of metastatic triple negative breast cancer (TNBC). An estimated 280,000 cases of breast cancer are diagnosed annually and 15–20% of these are TNBC. TNBC often affects younger patients (<40 years old) and disproportionately affects Black and Hispanic women. TNBC has a poor prognosis, rapidly progressing to distant metastases and developing resistance to chemotherapy. Because TNBC is negative for hormone receptors (HR-) and human epidermal growth factor receptor 2 (HER2-) biomarkers, current HR- and HER2-directed therapies are ineffective. In addition, most do not have identified markers (e.g., BRCA, PD-L1), precluding the use of other targeted therapies. As a result, conventional chemotherapy—which has poor tolerability and drug-resistance issues—is the standard of care for most late-stage TNBC patients. Overall, TNBC has a high rate of recurrence/metastasis, low survival rate, high treatment costs, and no cure. Thus, there is a critical need for novel treatments for late- stage TNBC. We have identified inhibition of the A2 purinergic receptors (A2R), A2AR and A2BR, as a promising strategy for overcoming the barriers of conventional TNBC therapies, including toxicity and drug resistance. Purinergic signaling is activated when adenosine binds to A2AR and A2BR, promoting cancer growth and suppressing anti-tumor immunity. We have identified several novel A2R inverse agonists with a unique mechanism of action (MOA), not only inhibiting adenosine-induced signaling, as do neutral antagonists, but also reducing basal-level signaling, resulting in more potent inhibition than neutral antagonists. Both in vitro and in vivo studies show that these compounds are orally bioavailable and effective inhibitors of tumor growth, migration, and metastasis in TNBC, while having no identified toxicities. While our current A2R inverse agonists exhibit strong efficacies, tolerability, and many favorable drug characteristics, they do have limitations, including low solubility, limited oral bioavailability, short half-life, and less than optimal stability in blood. In this application, we plan to address these limitations by optimizing these compounds through computer-aided and AI-based drug discovery technology including structure-based de novo design and large-scale analog screening, as well as further medicinal chemistry optimization by undertaking three specific aims: 1) Design and generate optimized A2R inverse agonists and evaluate potential improvements in drug properties, target affinity, efficacies, and anti- tumor immunity, 2) Perform PK analysis to select compounds with improved stability, oral bioavailability, and high levels of tumor tissue distribution and efficacy, 3) Evaluate dose-dependent efficacy and immune system effects in multiple mouse models. Success will identify and establish the resulting optimized drug candidate compound(s) as pioneering A2R dual inverse agonists, designed to treat TNBC, as well as a variety of immunogenic cancers. Our drug candidate with a novel MOA has the potential to benefit TNBC patients by improving their overall survival, particularly those ineligible for or resistant to current therapies.
